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BBC Two – 5 Ways to Save the World

Some ideas involve reducing the power of the sun and cooling the planet.Professor Roger Angel from Arizona – the designer of the world's largesttelescope – is proposing to put a giant glass sunshade in space whichwill deflect a small percentage of the sun's rays back into space.

Dutch Professor Paul Crutzen won the Nobel Prize for chemistry when hediscovered the causes of the hole in the ozone layer. His plan is tofire hundreds of rockets loaded with tons of sulphur into thestratosphere, creating a vast, but very thin, sunscreen of sulphuraround the Earth.

British atmospheric physicist Professor John Latham and engineer StephenSalter have designed a fleet of remote-controlled yachts. These wouldpump fine particles of sea water into the clouds, increasing thethickness of the clouds and reflecting the sun's rays.

Others want to tackle the problem of excess carbon dioxide – the causeof global warming. Sydney engineer Professor Ian Jones proposes to feedplankton – tiny plants and animals that live in the sea – with tons offertiliser. This will make the plankton grow and absorb carbon dioxidefrom the air.

New York-based Professor Klaus Lackner has designed a machine to capturecarbon dioxide. His plan is to locate them across the globe where theywould suck in carbon dioxide, turning it into a powder to be buried deepunder the ocean in disused oil or gas fields.